Clicking the image to see the high-res version shows that the six PCIe slots are electrically x16/x1/x16/x1/x8/x8 with "M.2 x4" printed on the board. It would make sense for them to put the M.2 x4 on the MCH since it's an SLI board. They have to presume people want x16/x16/x8 and M.2 at the same time. The board could also run x16/x8/x8/x8 and the M.2 slot at the same time. If you only want one GPU in there, you could add four other cards (1x1 and (3x4 or 3x8)) and the GPU will still use x16.Reply